Frigate "Changzhou" sets sail at a port in Zhoushan, east China's Zhejiang Province, July 3, 2012. The 12th Chinese naval escort flotilla, consisting of frigate "Yiyang", frigate "Changzhou" and comprehensive supply ship "Qiandaohu", departed from Zhoushan on Tuesday for the escort mission in the Gulf of Aden and Somali waters to protect commercial ships from pirate attacks. [Xinhua]